Finding Lambda 4 for mechanical harmonics

[Iwanttolearn7]

Homework Statement

I am trying to find the equation for lambda four for mechanical harmonics.

Homework Equations

I know that lambda1=2L, lambda2=L, lambda3=2L/3, but neither google nor my textbook have the equation for lambda4!

The Attempt at a Solution

I have searched my physics textbook, class notes, and google for this and have come up with absolutely nothing.
Can anyone please assist? I would greatly appreciate it!
Thank you!

 

[Iwanttolearn7]

OH my gosh I'm such a dork. Lambda4= 2L/4, I figured out the pattern all by my lonesome. Geez, I'm bad at physics!